Background: Social referencing (SR) refers to infants' use of caregivers as emotional guides to help them interpret ambiguous situations as safe or threatening. Understanding SR can advance our knowledge of infant social cognition and establish early markers of developmental disorders. For example, older children with autism are less likely to use caregivers as social referents (Walden, 1993). Most studies have been conducted with infants who are ambulatory, a criterion of the classic SR paradigm, therefore ignoring younger infants. This has hindered our knowledge of possible early mechanisms of emotion regulation. In addition to advancing knowledge of infant social-emotional development, the proposed studies will assist in developing a new research paradigm for studying SR in not-yet-ambulatory infants. Objective and Aims: The proposed studies will track the emergence of SR in 4-to 6- month-olds, as well as demonstrate that 6-month-olds' emotional responses are influenced by parental emotion (fear or joy) during ambiguous situations. We will also show that 6-month-olds rely more on parental emotion (fear or joy) than contextual cues during unambiguous (i.e., frightening or funny) events. We hypothesize that infants will mirror parents' affect (fear/joy) through a variety of modalities (facial expression, behavioral approach/avoidance, and heart rate) during both ambiguous and unambiguous events, and predict that infant temperament will moderate the effect of parental emotion on infants' responses (infant approach/avoidance, heart rate, and joy/fear). Research Design: Sixty 4-month-olds will watch a parent presented with ordinary and ambiguous/absurd events during which parents will respond with joy or neutrality. The procedure will be repeated at 5 months old. At 6-months, the same infants will observe a parent presented with an ambiguous object while responding with facial and vocal cues of fear/joy in counter-balanced order. Sixty additional 6-month-olds will observe a parent presented with potentially frightening and funny objects, while providing congruent or incongruent emotional cues in a within-subjects design. In both studies, infants' SR, affect (negative/positive), behavior (avoidance/approach), and heart rate will be measured. Infant gender and temperament will be investigated as moderating variables. Sequential analysis (Bakeman & Gottman, 1997) will be used to understand the dynamic sequence that underlies infant affective response during parent-infant social interaction. PUBLIC HEALTH RELEVANCE: This research may establish the early influence of social referencing, and thus has implications for identifying an early marker of developmental disorders. It may increase knowledge of emotion regulation in infants, including risk for affective disorders.